There continues to be an increasing demand for the production of highly pure materials such as silicon, titanium, iron, nickel, boron, gallium, etc. For instance, there is a soaring demand for high grade, pure silicon for use in the semiconductor and solar cell industries. Additionally, specialty alloys, such as those of titanium, TiV4Al6 and similar alloys, which are strong and lightweight, are widely used throughout the aerospace and defense industries. Manufacturing methods currently employed for the production of high purity materials, such as silicon and titanium, are energy intensive, costly, and generate a significant amount of excess product (e.g., Si or Ti fines) that is either commercially unusable or it requires significant reprocessing.
For example, in many instances, the production of both silicon and titanium results in the generation of a large quantity of fine silicon or titanium powder that is typically unusable in the further production of the high grade material. For instance, the trichlorosilane method of silicon production, wherein metallurgical grade silicon is contacted with HCl to produce trichlorosilane and then the trichlorosilane is converted back to pure silicon by reduction with hydrogen, using filament type reactors, requires over 100 Kwh/kg of silicon. In an effort to decrease the energy consumption, new fluidized bed reactors are being used, but they produce approximately 20% unusable fines that are difficult to consolidate and, therefore, results not only in the production of a highly pure electronic grade pellet, but also in the generation of 10 to 20% of a fine silicon powder having an average particle diameter in the sub-microns. In the Ti industry, the Kroll process is being substituted by other processes such as the Armstrong process for the production of high grade titanium which also results in the generation of a large quantity of excess titanium powder also having an average particle diameter in the sub-microns. Equally, the electrochemical deoxidation of TiO2 results in the generation of very fine particles of Ti.
The use of such fine grain silicon and titanium powders in the further production of high grade materials is difficult because the fine particulate matter has a high surface to volume area making them good thermal insulators. Hence, it is hard to consolidate these materials because the heat applied in the consolidation process is not readily transferred to the core of the particles but is rather dispersed throughout the surface of the bulk material. Another complication with respect to the purification and consolidation of reactive materials (such as metals) is that fine powders of such metals are highly reactive with the oxygen in air, resulting in the generation of a thick oxide coating on the surface of the metal particles, which oxide coating further prevents the metal particles from consolidating.
Accordingly, there is a need for a process that makes use of such fine powders in the production of high grade, pure consolidated materials that can be further processed into useful forms by conventional processes such as extruding, forging, milling, machining. The present invention meets those and other such needs.